1. Field of the Invention
The present invention relates to a magnetic recording medium of a heat-assisted magnetic recording type or a microwave-assisted magnetic recording type which is used in a hard disk drive (HDD) and the like, and a magnetic recording and reproducing apparatus.
Priority is claimed on Japanese Patent Application No. 2012-189237, filed on Aug. 29, 2012, the content of which is incorporated herein by reference.
2. Description of Related Art
In order to increase the recording capacity of a hard disk drive, an increase in the recording density of a medium has been progressed. However, it is difficult to increase the recording density of a medium due to a problem, referred to as a so-called trilemma, that it is difficult to simultaneously establish particle size fineness, thermal stability characteristics, and recording characteristics. Heat-assisted magnetic recording types are expected as a method of solving such a trilemma, and research development has been actively conducted.
The heat-assisted magnetic recording type is a recording type that reduces a medium coercive force and performs writing, by irradiating a medium with near-field light using a magnetic head, and locally heating the medium surface.
Materials having high crystal magnetic anisotropy Ku are used in a medium magnetic layer of this heat-assisted magnetic recording type, thereby allowing the volume of a magnetic particle to be reduced in a state where KuV/kT (Ku: magnetic anisotropy constant, V: particle volume, k: Boltzmann constant, and T: temperature) which is a thermal stability index is maintained.
As such high Ku materials, ordered alloys such as FePt (Ku to 7×107 erg/cm3) and CoPt (Ku to 5×107 erg/cm3) having an L10-type crystal structure are known.
In order to obtain a heat-assisted magnetic recording medium exhibiting high crystal magnetic anisotropy, it is necessary to cause an alloy of a magnetic layer having an L10-type crystal structure to have a good (001) orientation. Since the orientation of the magnetic layer is controlled by an under layer, it is necessary to appropriately select a material of the under layer.
For example, Japanese Unexamined Patent Application, First Publication No. H11-353648 discloses that a FePt magnetic layer exhibits a (001) orientation by using a MgO under layer. In addition, J. Appl. Phys., Vol. 109, 07B770 (2011) discloses that a FePt magnetic layer exhibits a good (001) orientation by using a RuAl under layer and a TiN under layer.
In addition, as another technique which is attracting attention as a next-generation recording type, there is a microwave-assisted magnetic recording type. The microwave-assisted magnetic recording type is a type of inclining a magnetization direction from a magnetization easy axis by irradiating a magnetic layer of a magnetic recording medium with microwaves, and recording magnetic information by locally switching the magnetization of the magnetic layer.
In the microwave-assisted magnetic recording, such as a heat-assisted magnetic recording, it is also possible to use a high Ku material, made of an alloy having an L10-type crystal structure, as a material of the magnetic layer. It is essential to reduce the particle size of the magnetic layer in order to further improve recording density. For that reason, in the microwave-assisted magnetic recording type, a magnetic recording medium is also required which is made of an alloy having an L10-type crystal structure capable of maintaining thermal stability even when the size of a magnetic particle is reduced.